1. Field of the Invention
The present invention relates generally to processing of geological data and more particularly to normalization of well log curves.
2. Description of the Related Art
The geology of a borehole may be explored using borehole logging tools. Measurements of various properties of the subsurface formations through which the borehole penetrates can be made, and a log of the measurements against depth can be produced. This borehole data is collected via a number of techniques including resistivity/conductivity measurements, ultrasound, NMR, and gamma radiation, for example. Generally, borehole data is analyzed by human interpreters in order to characterize a subsurface geological formation to allow decisions to be made regarding potential of the well or to determine information about the nature of the surrounding geologic area. Borehole data of this type may be used to replace or supplement the collection of cores for direct inspection.
As with any measurement, well logging is subject to various causes of noise. For example, sensor noise (including, e.g., shot noise), sensor drift and other effects can cause logs to appear different from a theoretical sensor response.
As a number of different wells are logged, accounting for noise can allow a more accurate comparison between logs, providing a more useful understanding of the subsurface geology. In particular, where automated analysis methods are to be applied to the well logs, such normalization can help to reduce incorrect conclusions resulting from, for example, a gain change of the sensor between logging operations.